ENGG*3070 – Assignment No. 2 (Due
Saturday, October 23, XXXXXXXXXX:59 pm)
Marking:
Only selected problems will be marked in detail and the
emaining will be checked for completeness and
co
ectness of final answers.
The neatness and organization of your assignment
eport has a significant weight.
• The due date for this assignment is extended from Oct 18
to Oct 23.
• Moreover, the drobox will remain open for late
submission without penalty until October 25, 11:59 PM.
• Late submission after the grace period (Oct 25) will not
e accepted unless academic consideration is granted.
• NOTE: There are a total of 10 problems to be solved, and
as such you need to start working on this assignment as
early as possible.
Problem No. 1 (Manual Assembly Line)
A manual assembly line is to be designed to make a small consumer product. The
work elements, their times, and precedence constraints are given in the table
elow. The workers will operate the line for 400 min per day and must produce
300 products per day. A mechanized belt, moving at a speed of 1.25 m/min, will
transport the products between stations. Because of the variability in the time
equired to perform the assembly operations, it has been determined that the
tolerance time should be 1.5 times the cycle time of the line. (a) Determine the
ideal minimum number of workers on the line. (b) Use the larges candidate rule
to balance the line. (c) Use the Kil
idge and Wester method to balance the line.
(d) Use the ranked position to balance the line. (e) Compute the balance delay in
part (b) (c), and (d).
Problem No. 2 (Manual Assembly Line)
Two models, A and B, are to be assembled on a mixed-model line. Hourly
production rates for the two models are: A, 25 units/hr; and B, 18 units/hr. The
work elements, element times, and precedence requirements are given in the
table below. Elements 6 and 8 are not required for model A, and elements 4 and 7
are not required for model B. Assume E = 1.0, Er = 1.0, and Mi = 1. (a) Construct
the precedence diagram for each model and for both models combined into one
diagram. (b) Find the theoretical minimum number of workstations required to
achieve the required production rate. (c) Use the Kil
idge and Wester method to
solve the line balancing problem. (d) Determine the balance efficiency for your
solution . (d) Determine the variable launching internal of each model, and
provide a typical variable launching sequence and the time of each launch. (e)
Determine the fixed rate launching interval, and the launch sequence of models A
and B during for the first 10 launches (Note: the complete answer which you are
not required to provide should list a total of 45 launches and can be better done
using excel).
Problem No. 3 (Manual Assembly Line)
Three models A, B, and C are to be assembled on a mixed-model line. Hourly
production rates for the three models are: A, 15 units/hr; B, 10 units/hr; and C, 5
units/hr. The work elements, element times, and precedence requirements are
given in the table below. Assume E = 1.0, Er = 1.0, and Mi = 1. (a) Construct the
precedence diagram for each model and for all three models combined into one
diagram. (b) Find the theoretical minimum number of workstations required to
achieve the required production rate. (c) Use the Kil
idge and Wester method to
solve the line balancing problem. (d) Determine the balance efficiency for the
solution. (e) Determine the fixed rate launching interval and the launching
sequence of models A, B and C during 1 hour production.
Problem No. 5 (Manual Assembly Line)
A moving belt line is used to assemble a product whose work content = 22 min.
Production rate = 35 units/hr, and the proportion uptime = 0.96. The length of
each station = 2.0 m and station manning level = 1.0 for all stations. The belt
speed can be set at any value between 0.6 and 3.0 m/min. It is expected that the
alance delay will be about 0.08 or slightly higher. Time lost for repositioning each
cycle is 6 sec. (a) Determine the number of stations needed on the line. (b) Using
a tolerance time that is 50% greater than the cycle time, what would be an
appropriate belt speed and spacing between parts?`
Problem No. 6 (Transfer Line)
A 30-station transfer line has an ideal cycle time of 0.75 min, an average
downtime of 6.0 min per line stop occu
ence, and a station failure frequency of
0.01 for all stations. A proposal has been submitted to locate a storage buffer
etween stations 15 and 16 to improve line efficiency. Determine (a) the cu
ent
line efficiency and production rate, and (b) the maximum possible line efficiency
and production rate that would result from installing the storage buffer.
Problem No. 7 (Transfer Line)
In Problem 6, if the capacity of the proposed storage buffer is to be 20 parts,
determine (a) line efficiency, and (b) production rate of the line. Assume that the
downtime (Td = 6.0 min) is a constant.
Problem No. 8 (Transfer Line)
An eight-station rotary indexing machine performs the machining operations
shown in the table below, with processing times and
eakdown frequencies for
each station. Transfer time is 0.15 min. A study of the system was undertaken,
during which time 4,000 parts were completed. The study also revealed that
when
eakdowns occur, the average downtime is 7.5 min. For the study period,
determine (a) average hourly production rate, (b) line uptime efficiency, and (c)
how many hours were required to produce the 4,000 parts.
Station Process Process time Breakdowns
1 Load part 0.50 min 0
2 Mill top 0.85 min 22
3 Mill sides 1.05 min 31
4 Drill two holes 0.60 min 47
5 Ream two holes 0.43 min 8
6 Drill six holes 0.92 min 58
7 Tap six holes 0.75 min 74
8 Unload part 0.40 min 0
Problem No. 9 (Transfer Line)
A 16-station transfer line can be divided into two stages by installing a storage
uffer between stations 8 and 9. The probability of failure at any station is 0.01.
The ideal cycle time is 1.0 min and the downtime per line stop is 10.0 min. These
values are applicable for both the one-stage and two-stage configurations. The
downtime should be a considered constant value. The cost of installing the
storage buffer is a function of its capacity. This cost function is ?? = $0.60?
hr = $0.01?/min, where ? = the buffer capacity. However, the buffer can only
e constructed to store increments of 10 (in other words, ? can take on values of
10, 20, 30, etc.). The cost to operate the line itself is $120/hr. Ignore material and
tooling costs. Based on cost per unit of product, determine the buffer capacity ?
that will minimize unit product cost.
Problem No. 10 (Transfer Line)
A proposed synchronous transfer line will have 20 stations and will operate with
an ideal cycle time of 0.5 min. All stations are expected to have an equal
probability of
eakdown, p = 0.01. The average downtime per
eakdown is
expected to be 5.0 min. An option under consideration is to divide the line into
two stages, each stage having 10 stations, with a buffer storage zone between the
stages. It has been decided that the storage capacity should be 20 units. The cost
to operate the line is $96.00/hr. Installing the storage buffer would increase the
line operating cost by $12.00/hr. Ignoring material and tooling costs, determine
(a) line efficiency, production rate, and unit cost for the one-stage configuration,
and (b) line efficiency, production rate, and unit cost for the optional two-stage
configuration (assume a constant repair time).